A $160 million plan to hide part of the region’s biggest light-rail line in a recreational corridor of Minneapolis confronts a major hurdle Wednesday that could determine whether it lurches forward or stalls.

Metro leaders are poised to sign off on digging nearly half-mile-long tunnels for the light rail on either side of a water channel, where the trains would emerge for 360 yards to approach and cross a bridge.

Deemed less disruptive than both more- and less-costly alternatives, the tunnel plan still faces fierce opposition from some in Minneapolis who say the trains surface for too long and who distrust assurances that bike trails and lakes will be preserved.

Minneapolis Mayor R.T. Rybak is expected to appear at Wednesday’s meeting of metro leaders and react to the plan, but it won’t be the final word from the city. Neighborhood opposition to the tunnels could prompt the city to withhold its consent later this fall for the entire light-rail project from downtown to the southwest suburbs, a move that would threaten its future.

The plan was a topic of private conversation this week at a conference of urban officials in Arizona attended by Rybak, Hennepin County Commissioner Peter McLaughlin, and Metropolitan Council Chair Susan Haigh, whose agency is overseeing the project.

The Twin Cities officials huddled between conference sessions to talk about how to salvage the Southwest project, McLaughlin said.

“There was a lot of conversation about how do we work this thing through,” he recalled. “There’s a sense that … this is very important for the region, there really is a need to find a way to make sure this thing doesn’t collapse.”

Gov. Mark Dayton will wait for the metro leaders to make a recommendation on the plan before offering his own opinion.

“He said this advisory group that is voting [Wednesday] has been putting all sorts of time and energy into this and he certainly wants to benefit from the result of that process before weighing in,” Bob Hume, Dayton’s deputy chief of staff, said Tuesday. The Met Council is expected to act on the recommendation next week.

The tunnels and other cost increases would bring the estimated price of the Southwest Corridor light rail to $1.55 billion, up from an earlier estimate of $1.25 billion.

Not long ago, tunnels weren’t even on the drawing board for the Southwest Corridor light rail. But planners desperate to keep the project on track designed the mini-subways as an alternative to moving freight trains from Minneapolis to St. Louis Park to make room for the light rail. The St. Louis Park idea was virtually discarded after the suburb and some of its homeowners objected to putting the freight trains on two-story berms to satisfy a railroad’s demands for smoother grades. Metro officials also balked at the $200 million price tag for the freight reroute.

Rybak and other Minneapolis officials have long insisted on rerouting the freight trains to St. Louis Park in exchange for accepting the light rail in the Kenilworth corridor. But the mayor hasn’t recently ruled out supporting the tunnels under some circumstances.

The mayor has faulted the Met Council for rejecting calls to explore new options for rerouting the freight, and the current proposal calls for abandoning any future efforts to do so. He could vote for or against the plan or abstain on Wednesday.

Pros and cons

The Metropolitan Council says the tunnels are the least obtrusive of several options. Rerouting trains to St. Louis Park would have required removal of 30 properties there. Keeping the freight in Minneapolis and burying the light rail nearby would spare those St. Louis Park properties. It also would spare Minneapolis townhouses that otherwise would be razed to make room for the transit if it were built at ground level next to freight and recreational trails in the narrowest part of the corridor south of Cedar Lake Parkway.

Some homeowners along the corridor would see the light rail when it emerged from the tunnels for 20 seconds to approach and cross the bridge.

But about 220 trains would cross daily. And the tunnels wouldn’t be bored from underground but dug from above and covered, work that would require removal of 1,000 trees and relocation of the bike trail for perhaps two years.

Unlike the southern tunnel, the northern tunnel would run a half mile through a wider parklike stretch of the corridor, where there is more room to locate light-rail above ground next to freight and trails. The northern tunnel would end north of 21st Street, sacrificing plans for a station that is projected to serve an average of 1,652 riders a weekday.

Some regional officials have suggested cutting the northern leg to spare the station and shave $60 million off the $160 million tunnel cost. Officials also explored running the light rail through the entire corridor at ground level next to the freight and trails, or elevating the trails above them. Either of those options would cost about $55 million. All of those ideas draw even stronger opposition in Minneapolis and have been cast aside, as least for now.

Earlier this week, Amazon announced that it's hiring 1,000 more full-time workers at its Shakopee fulfillment center. But city and county officials are still assessing reliable transportation options for the 1,500 people who already work there.